The Japanese consulate general in Los Angeles was found to have sent a letter of protest to a Korean American who put up a billboard advertisement on an L.A. highway expressing Korean sovereignty over the Dokdo islets.

In the letter dated April fifth, the consulate general said that “Takeshima,” the Japanese name for Dokdo, is Japan's territory, historically and under international law, adding that this was the official opinion of Tokyo's foreign ministry.

It asked that the advertisement be taken down.

Alex Cho, CEO of Diamond Family Spa in eastern L.A., first put up the ad on Highway 60 on January 15th. The ad reads "Dokdo Island Belongs to Korea."

In a phone interview Sunday, Cho said he was very displeased to receive the letter. He added that he's considering extending the advertisement, which expires this month, until the end of May.